querier: drop redundant detachChunksFromBuffer copy - #7773
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August 16, 2026 03:34
trimStringByBytes scans backwards from the truncation point to find a
UTF-8 rune start, but the loop had no lower bound. When a request field
consists only of UTF-8 continuation bytes (0x80-0xBF) there is no rune
start to land on, so size underflows past zero and bytesStr[-1] panics
with 'index out of range [-1]'. Because the active query tracker is
enabled by default and the panic happens on a goroutine without recover(),
an attacker-supplied match[]/query value can crash the querier.
Bound the scan with 'size > 0' so it stops at the start of the string
instead of underflowing. When no rune start exists the field is truncated
to an empty string, which is safe.
Add TestTrimForJsonMarshalContinuationBytes covering the all-continuation-
byte case; existing multi-byte tests use valid UTF-8 ('世') which always
terminates the scan at index 0 and therefore never exercised the underflow.
Fixes cortexproject#7729
Signed-off-by: ...
Signed-off-by: Mehrdad Biukian Naeini <mehrdad.biu@mtnirancell.ir>
…roject#7731) Signed-off-by: Mehrdad Biukian Naeini <mehrdad.biu@mtnirancell.ir>
…#7731) Signed-off-by: Mehrdad Biukian Naeini <mehrdad.biu@mtnirancell.ir>
Signed-off-by: Mehrdad Biukian Naeini <mehrdad.biu@mtnirancell.ir>
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Summary
Fixes #7732.
#7670 added a
detachChunksFromBuffercopy on the distributor queryable's ingester-read path, assuming chunkDataaliases the gRPC wire buffer. It does not: the gogo-generatedChunk.Unmarshaldoesm.Data = append(m.Data[:0], dAtA[iNdEx:postIndex]...), allocating a fresh slice perRecv. So the copy was a wasted allocation + memcpy, and because theQueryStreamResponsestays live for the wholestreamingSelectbody, the original and the copy are reachable at once — peak heap during the loop went up rather than down.This change removes
detachChunksFromBufferand passesresult.Chunksdirectly tochunkcompat.FromChunks, keeping only theFromLabelAdaptersToLabelsWithCopychange (label values do alias the buffer and still need detaching).Test plan
TestChunksDoNotAliasWireBuffer: marshals aQueryStreamResponse, unmarshals it, and asserts chunkDatais a distinct allocation from the wire buffer (the invariant that makes the copy unnecessary), and that querying returns the correct bytes.TestIngesterStreamingand the rest ofpkg/querierstill pass.with_detachbenchmark subtest (it exercised the deleted function); thewithout_detachpath now matches production.Checklist
Signed-off-by: mehrdadbn9 mehrdadbn9@users.noreply.github.com